fix comment

src/os/unix/ngx_gcc_atomic_x86.h

diff --git a/src/os/unix/ngx_gcc_atomic_x86.h b/src/os/unix/ngx_gcc_atomic_x86.h
index 27c353d..1951d00 100644
--- a/src/os/unix/ngx_gcc_atomic_x86.h
+++ b/src/os/unix/ngx_gcc_atomic_x86.h
@@ -122,5 +122,5 @@
 
 #define ngx_memory_barrier()    __asm__ volatile ("" ::: "memory")
 
-/* old as does not support "pause" opcode */
+/* old "as" does not support "pause" opcode */
 #define ngx_cpu_pause()         __asm__ (".byte 0xf3, 0x90")